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O Level Biology (5090)
Unit 7: Organisms and the Environment
Recommended Prior Knowledge
Students should have a knowledge of the different forms of energy, of plant nutrition, respiration and transpiration. A knowledge of the great diversity of life and habitats
would be helpful.
Context
This Unit, whilst considering some of the fundamental topics of biology also takes a broader view of the subject and investigates some of the ethical issues raised by
human interference with the environment.
Outline
Energy flow is traced through biological systems and the carbon and nitrogen cycles are considered in some detail. There is a reference to parasitism in the shape of
the transmission and control of malaria, but control measures employed lead into a consideration of the human effect on the ecosystem in a wider sense –
deforestation, pollution and damage to habitats leading to a need for conservation.
AO
Learning outcomes
Suggested activities and further guidance
15(a)
State that the Sun is the
principle source of energy
input into biological systems.
Stress that it is light energy from the Sun which is
important in photosynthesis, but enzymes controlling all
metabolic reactions rely also on its heat energy to provide
a suitable temperature for their operation.
Online resources
Other resources
Textbooks
Ian J. Burton – Topic 17
The Relationship
between Organisms and
the Environment
Mary Jones – Unit 16
Organisms and
Environment
M. & G. Jones – 15
Living organisms and
their environment
15(b)
Describe the non-cyclical
nature of energy flow.
Once energy is released by organisms it is lost and can
be replaced only by further input, directly or indirectly,
from the Sun.
1
15(c)
15(d)
Define the following terms and
establish the relationship of
each in food webs: producer,
consumer, herbivore,
carnivore, decomposer, food
chain.
Describe energy losses
between trophic levels and
infer the advantages of short
food chains.
Students may be able to suggest food chains in various
different habitats.
Students should be provided with a food chain of at least
three organisms, starting with a producer, and write each
of the specified words underneath the appropriate
component of the food chain provided.
In Unit 8(d) of unit 4 students considered the use of
energy for different processes in a body thus there is
always less energy available to each successive level in a
food chain or web.
Food chains and terminology:
http://www.bbc.co.uk/schools/gc
sebitesize/science/add_aqa/food
chains/foodchains1.shtml
Energy transfer:
http://www.bbc.co.uk/schools/gc
sebitesize/science/add_aqa/food
chains/foodchains2.shtml
Use the suggested online resource to review the ways in
which energy may be lost between trophic levels.
Students may make a bullet-point list of these and explain
why food chains are commonly limited in length.
The efficiency of food production in terms of placing
humans as primary consumers and of reducing energy
losses through factory farming may be discussed with
reference to named examples generated by students.
15(e)
Describe and interpret
pyramids of numbers and of
biomass.
It should be explained why pyramids of biomass (which
are of typical pyramid shape) provide a more accurate
representation of energy relationships between organisms
in a food chain or food web than pyramids of numbers
(many of which are not the typical pyramid shape).
Students may draw and explain pyramids of number and
biomass for food chains introduced earlier in the unit.
They may link the shape of biomass pyramids to the
knowledge gained in 15(d).
Students may draw pyramids to scale using graph paper if
numbers and/or biomasses are given.
2
Pyramids of biomass:
http://www.bbc.co.uk/schools/gc
sebitesize/science/add_aqa/food
chains/foodchains3.shtml
15(f)
Describe and state the
importance of the carbon
cycle.
This outcome stresses the fact that life is carbon-based
and is an opportunity to consolidate topics covered in
Units 2, 3 and 4.
Students may list and then arrange into a sequence all the
processes they have studied which involve carbon
compounds. The cyclical nature of these processes
should become apparent.
The carbon cycle info and diag.:
http://www.bbc.co.uk/schools/gc
sebitesize/science/add_aqa/food
chains/foodchains5.shtml
Carbon cycle animated video:
http://www.bbc.co.uk/schools/gc
sebitesize/science/add_aqa/food
chains/foodchainact.shtml
Students may be asked to trace the fate of an atom of
carbon after it has entered a plant in a CO2 molecule
during photosynthesis, thus building up their own carbon
cycles. These may then combined to provide (perhaps
with a few additions/adjustments) the definitive version for
distribution.
The suggested online resources may be used to provide
additional stimuli and assistance during or following the
above activities.
15(g)
Describe the nitrogen cycle in
making available nitrogen for
plant and animal protein,
including the role of bacteria in
nitrogen fixation,
decomposition and nitrification
(details of denitrification and
the names of individual
bacteria are not required).
Students may attempt to brainstorm the nitrogen cycle in a
similar way to the carbon cycle. Cross reference with
decomposition considered in 14(b) of Unit 6.
Students tend to find this cycle difficult to understand and
remember. It is therefore wise to avoid unnecessary
detail. The suggested online resources present the topic
at an appropriate level.
Simple nitrogen cycle diagrams:
http://www.scool.co.uk/gcse/biology/environ
ment/cycling-throughnature.html#nitrogen-cycle
Students may use the talking explanation of the nitrogen
cycle to write a set of bullet-point notes to explain each
step – underlining the different types of bacteria involved.
Talking explanation and
animation of the nitrogen cycle:
http://www.nodvin.net/snhu/SCI2
19/demos/Chapter_3/Chapter_0
3/Present/animations/32_2_1a.h
tml
Distinguish carefully between the terms ‘nitrogen fixation’
and ‘nitrification’. Reference should be made to bacteria in
the root nodules of leguminous plants as well as to those
which are free-living.
Photograph of root nodules:
http://blog.lib.umn.edu/denis036/
thisweekinevolution/AlfalfaNodul
es5.jpg
3
15(h)
Understand the role of the
mosquito as a vector of
disease.
Indicate how the lifestyle of the mosquito makes it a
successful vector of a wide variety of diseases. Stress that
the mosquito is the carrier (vector) of the pathogen but
does not itself cause malaria. Ways in which control of the
mosquito vector is achieved should be considered here.
Students may use the suggested online resources to
research the lifestyle and control of the mosquito vector
and present their findings in the form of a poster, fact
sheet or brief presentation to the class.
Mosquito vector and control:
http://www.cdc.gov/malaria/abou
t/biology/mosquitoes/index.html
Textbook
M. & G. Jones - 13
Health, disease and
medicine
World Health Organisation
malaria fact sheet:
http://www.who.int/mediacentre/f
actsheets/fs094/en/index.html
It is possible for some students to research and
summarise 15(h) whilst others do so for 15(i). Students
may subsequently share their findings.
15(i)
15(j)
Describe the malaria pathogen
as an example of a parasite
and describe the transmission
and control of the malarial
pathogen (details of the life
cycle of the pathogen are not
required).
Control of the pathogen both before and after it has
entered the body should be considered here.
Describe the effects of humans
on the ecosystem with
emphasis on examples of
international importance
(tropical rain forests, oceans
and important rivers).
Action which affects large areas in one part of the world
may have consequences in another (e.g. global warming,
scarcity or contamination of fish supplies). Loss of habitats
leads to extinction of species and to loss of possible
benefits from those species (e.g. drugs). Action taken in
one region near a river can cause flooding and
devastation hundreds of miles away.
See suggested resources listed
above.
As above, students may use the suggested online
resources to research the lifestyle and control of the
mosquito vector and present their findings in the form of a
poster, fact sheet or brief presentation to the class.
Students may be divided into three groups with each
group studying in depth, using the suggested online
resources, one example of the effects of humans on the
ecosystem. Students may present their findings in the
form of a report or presentation to exchange with others.
4
Tropical rain forests:
http://environment.nationalgeogr
aphic.com/environment/habitats/
rainforest-threats/
Textbooks
Mary Jones – Unit 17
Human Effects on
Ecosystems
Oceans:
http://www.protectplanetocean.o
rg/introduction/introduction.html
Ian J. Burton – Topic 18
– The Effects of Human
Activity on the
Ecosystem
Rivers:
http://www.internationalrivers.or
g/
M. & G. Jones – 16
Humans and the
environment
15(k)
Describe the consequences of
deforestation in terms of its
effects on soil stability, climate
and local human populations.
The removal of trees removes the binding effect their
roots have on the soil as well as the protection their
canopies provide from sun, wind and rain. The humus
their dead leaves provide is also lost. Local populations
may lose homes and livelihoods. Climate changes are
usually experienced at greater distances from the site of
deforestation.
Deforestation:
http://www.bbc.co.uk/dna/h2g2/
A3556848
Students may use the list of points outlined above and the
suggested online resource to produce a ‘spider diagram’
showing the consequences of deforestation.
15(l)
Evaluate the effects of:
water pollution by sewage, by
inorganic waste and by
nitrogen containing fertilisers;
air pollution by greenhouse
gases (carbon dioxide and
methane), contributing to
global warming;
air pollution by acidic gases
(sulphur dioxide and oxides of
nitrogen), contributing to acid
rain;
Students should be made aware of the damage being
caused to the planet by the stated forms of pollution and
that it is when the materials mentioned are used or
released in excess that problems occur.
Eutrophication should be considered as an effect of water
pollution by sewage and N2 fertilisers, as should the build
up along food chains of insecticides which cannot be
metabolised.
Ensure that there is a clear distinction in students’ minds
between the use of fertilisers and the use of insecticides.
Students may produce a set of flow charts to list the steps
involved in the processes of eutrophication, global
warming and the production of acid rain.
pollution due to insecticides.
Students may produce a poster or information leaflet
describing the effects of the stated forms of pollution.
The distinction between ‘causes’ and ‘consequences’ may
be clearly made by asking students to list these in two
columns of a table for each form of pollution.
5
Water pollution:
http://www.waterpollution.org.uk/
Combustion products:
http://www.bbc.co.uk/schools/gc
sebitesize/science/21c/atmosph
ere/chemicalreactionsrev2.shtml
Greenhouse effect animation:
http://earthguide.ucsd.edu/earth
guide/diagrams/greenhouse/
Acid rain:
http://www.supergreenme.com/g
o-green-environment-eco:AcidRain
15(m)
15(n)
Discuss reasons for
conservation of species with
reference to maintenance of
biodiversity, management of
fisheries and management of
timber production.
Many of the points relevant here will have been
considered in 15(j) and (k) above. The concept of
sustainable management of fish (via ‘quotas’) and timber
supplies should be promoted.
Discuss reasons for recycling
materials, with reference to
named examples.
Depletion of the planet’s resources is of concern.
Deforestation for paper production may be reduced by
paper recycling and energy may be saved by recycling
glass. Recycling metal (from cans to cars) saves both
energy and reduces the need to mine the ore.
Species conservation:
http://www.admwebstudios.co.u
k/Biodiversity3.htm#preserve
Students may research specific examples of species or
ecosystems which are actively being conserved, the
methods by which this is being achieved and the reasons
why their conservation is important. Students may present
their findings in a variety of formats.
The suggested online resource may be used by students
to research the topic further. Students may produce a
poster or information leaflet, for use in their school or
community, to promote the benefits of recycling.
6
Metal, paper, plastic and glass
recycling:
http://www.thriftyfun.com/tf4255
2953.tip.html